Study On The Mechanism And Characteristics Of Zero-valent Iron-manganese Bimetallic Material Synergistic Oxidant For Removing Thallium From Wastewater

Thallium?Thallium,Tl?is a rare,poisonous metal element with philophile and sulfur affinity,often associated with pyrite,lead-zinc ore and other minerals.With the development of China's smelting industry,thallium pollution incidents have occurred from time to time.The state and Guangdong Province have successively issued strict industrial wastewater thallium pollutant discharge standards.For the treatment of wastewater containing thallium,common methods include adsorption,ion exchange,precipitation,and liquid extraction.Among them,the adsorption method has the advantages of high efficiency,easy operation,high selectivity to heavy metal ions,easy separation,renewable utilization,and simple preparation of adsorption materials.?1?A systematic study on iron-manganese bimetals in conjunction with hypochlorite oxidation adsorption to remove thallium in wastewater.?1?The 3-ZVIMn composite material?the molar ratio is Fe/Mn=3/1?was prepared by the one-pot reduction method of sodium borohydride.The SEM image showed a flaky and interlaced structure mixed with spherical particles.The flake nanoplate is nZVMn.SAED?Selective Area Electron Diffraction?and HRTEM?Transmission Electron Microscope?images indicate that this 3-ZVIMn material has low crystalline properties.SEM-EDS element map shows that the preparation material mainly contains iron,oxygen and manganese.And from the element mapping results,it can be seen that 3-ZVIMn particles are susceptible to surface oxidation,and iron/manganese oxides are attached to their morphological shells,which is a common phenomenon in the synthesis of nano-scale zero-valent metal materials.?2?The prepared 3-ZVIMn composite material was used in conjunction with sodium hypochlorite to remove thallium.It was found that the treatment process was related to pH.When the pH of the solution was>7,the system could achieve rapid thallium removal.With0.01 mol/L dilute hydrochloric acid solution,the thallium trioxide adsorbed on the surface of3-ZVIMn can be dissolved and eluted to achieve the purpose of regeneration of 3-ZVIMn.The possibility of reuse is tested,and with the synergy of hypochlorite,it can quickly and efficiently remove thallium.And the investigation shows that the ionic strength and humic acid have a certain inhibitory effect on the thallium removal process,the inhibitory intensity is:Mg²⁺>Ca²⁺>Na⁺,high concentration>low concentration.?3?The thermodynamic and kinetic studies show that the prepared 3-ZVIMn composite material cooperates with sodium hypochlorite to remove thallium adsorption isotherm to meet the Langmuir model,and the theoretical maximum adsorption capacity is 990.0 mg/g.3-ZVIMn reached equilibrium after 1 h adsorption of high concentration thallium?300 mg/L?,and the adsorption process satisfied the pseudo-second-order kinetic model.?4?The mechanism of 3-ZVIMn removal of Tl???was further studied.The original state,post-adsorption and regenerated samples of 3-ZVIMn material were characterized by means of SEM,HRTEM,EDS,XRD,ESR and XPS.The results show that 3-ZVIMn cooperates with NaClO to remove Tl???.The mechanism is mainly divided into three parts:?i?NaClO oxidizes Tl???to form Tl₂O₃ precipitates on the surface of the material and is adsorbed by 3-ZVIMn;?ii?Tl???Complexing with the surface hydroxyl group of the adsorbent;?iii?Tl???is electrostatically attracted by the negative point 3-ZVIMn?pH=10?.?2?A systematic study on the mechanism of the removal of thallium by the 1-ZVIMn composite material and three oxidants?H₂O₂,Na₂S₂O₈,NaClO??1?The 1-ZVIMn composite material?the molar ratio is Fe/Mn=1/3?was prepared by the same method.SEM image analysis showed that the composite material had agglomeration phenomenon,more grooves,larger specific surface area,and the spherical shape of n ZVI and The characteristics of the nZVMn interleaved structure of the board.HRTEM analysis showed that it was amorphous and amorphous.SEM-EDS element mapping showed that the surface was mainly Fe,Mn,O,proving that there was an oxide layer on the surface.?2?The isothermal adsorption process of Tn???removal by 1-ZVIMn and three different oxidants was discussed,which showed that the adsorption of 1-ZVIMn and H₂O₂ on Tl???was more in line with the Freundlich model;1-ZVIMn and Na₂S₂O₈ on Tl???The adsorption is more consistent with the Langmuir model;the adsorption of 1-ZVIMn and NaClO on Tl???is more in line with the Freundlich model;the order of the maximum fitting adsorption capacity of the three is:156.4 mg/g?NaClO/1-ZVIMn?>143.1 mg/g?Na₂S₂O₈/1-ZVIMn?>133.0 mg/g?H₂O₂/1-ZVIMn?.?3?The mechanism of the removal of Tl???by 1-ZVIMn synergistic oxidant was further studied.The methods of SEM,HRTEM,EDS,XRD,XPS and ESR were used to characterize and analyze the 1-ZVIMn composite before and after adsorption.The results showed that 1-ZVIM and Tl???can stimulate H₂O₂,Na₂S₂O₈ and NaClO oxidants to produce corresponding oxygen-containing free radicals(HO·,SO₄^?·,ClO·),thereby promoting the performance of Tl???oxidation to Tl???,increasing by the efficiency of 1-ZVIMn in addition to Tl???.